1. Field of the Invention
This invention relates to a roundness processing device for a slipper surface of a rocker arm which operates the suction and exhaust valves of an automotive engine, and more particularly to a roundness processing device for a slipper surface of a rocker arm capable of rounding the slipper surface of the rocker arm without forming roundness on the polishing surface of a grinding wheel, and automatically driving and controlling the drive mechanisms in mutual relationship so as to enhance the working efficiency and lower the manufacturing cost.
2. Description of the Prior Art
The conventional process of polishing, in a round shape, the slipper surface of a rocker arm for operating the suction and exhaust valves of an automotive engine was as shown in FIG. 15; that is, a disc-shaped grinding wheel e of which the outer circumference (polishing surface) b is in the same shape as the round shape of a slipper surface d of a rocker arm c was mounted on a rotary shaft a of a plane grinding machine, while said rocker arm c was supported on a supporting shaft f which crossed orthogonally with said rotary shaft a, and said rocker arm c was reciprocated in the direction of the supporting shaft f while rotating and driving said grinding wheel e, and, accordingly, the slipper surface b was reciprocated on the polishing surface b of the rotating grinding wheel e.
Therefore, the width W of said grinding wheel e was set broader than the width w in the rotating direction of said slipper surface d.
In this method, however, the following demerits were involved.
(1) Since the width W of the grinding wheel e is broader than the width w of the slipper surface d, only the portion of the grinding surface b contacting with the slipper surface d is worn out, and the entire sectional shape in the axial direction of the grinding surface b gradually becomes different from the round shape of the slipper d. As a result, the remaining portion without being worn of the polishing surface b must be polished by truing to remake into the round surface in the same shape as the stripper surface d, and it requires labor and cost, which leads to reduction of job efficiency and elevation of manufacturing cost.
(2) On the polishing surface b of the grinding wheel e, the portion broader than the slipper d does not contribute to the roundness processing of the slipper surface d, and must be ground and removed by truing as mentioned above, so that the material of the grinding wheel is consumed purposelessly, which also leads to elevation of manufacturing cost.
(3) When machining plural types of rocker arm differing in the size of roundness (the radius of curvature) of the slipper surface d, it is necessary to exchange and use, on every machining, the grinding wheel e having the polishing surface b suited to the roundness shape of the intended slipper surface d, or reshape the polishing surface b of the grinding wheel e into a new roundness shape.
In the former process, spare grinding wheels to be replaced must be prepared as many as round shapes to be processed, and the cost required for this preparation is enormous. In the latter process, not only are the labor and cost for truing needed, but also the life of the grinding wheel e itself is shortened because of the wasteful polishing and removing.
(4) Of the above machining steps, most steps including the mounting and dismounting of the rocker arm c on and off the support shaft f, and reciprocal motion of the rocker arm c were manual works. Accordingly, particularly at mass production site, together with the problems of the shape of the grinding wheel e, the job efficiency was extremely poor, and it was difficult to reduce the manufacturing cost notably.